This invention relates to the field of golf clubs. More specifically, it relates to a metal wood club with an improved club head.
The desire to improve one's golf game and increasing the player's competitive advantage have led to many improvements in the design of golf clubs over the years. A relatively recent development is that of the "metal wood". Traditionally, woods (clubs usually used for tee shots and longer fairway shots) have had heads made of hard wood, the preferred wood being persimmon. The tendency of wood to warp or split, however, coupled with increasing cost of material and labor, has led to the development of metal heads for the woods. Such metal woods typically comprise a hollow cast metal shell filled with a synthetic plastic foam material.
The metal wood has achieved a large measure of success in terms of acceptance in use by skilled golfers. Nevertheless, many golfers still prefer traditional, "wooden" woods, because of what they consider to be non-optimal weight distribution in metal wood heads. Specifically, a very important element of the club head design is the concentration of as much of the mass of the head as possible into the face of the club head in the portion of the head behind the face. This puts the mass of the head where it effectively contributes to energy imparted to the ball, rather than being merely "dead weight" that limits the velocity of the club head when it is swung. In other words, such a distribution of the mass in the club head increases the effective mass of the head, without increasing this total mass. Maximizing the effective mass of the head without significantly increasing its total mass results in a little or no loss in the achievable club head velocity. The result is greater shot distance, since the energy imparted to the ball by the club is proportional to the effective mass of the club head times the square of the club head velocity. Preferably the mass in the club head is distributed around the perimeter of the club face. Perimeter weighting gives the club a larger sweet spot. Thus the perimeter weighed club is more forgiving. That is, a golfer need not strike the ball in the center of the club face to project the ball in a straight path. The enlarged sweet spot of a perimeter weighted club face allows the golfer a larger margin of error when striking the ball. A hit off-center still achieves a straight shot.
Recently, metal woods have become larger and oversized metal woods are now very popular. It is desirable to maximize the size of the oversize club head without increasing the weight of the club head to achieve maximum distance and velocity. In producing an larger oversized metal club head, therefore, the walls of the club head are thinner than a normal size club to avoid increasing the weight of the larger club and reducing the swing velocity. The enlarged or oversized metal wood heads are therefore thinner than conventional clubs and thus more susceptible to failure by cracking or crushing.
The top of the metal club head or crown in some oversized heads, is so thin that a golfer may crush or crack the metal club head by stepping on the crown. Some manufacturers of oversized clubs will not warrant against these types of failures. The metal club head is also subject to failure at the crown by cracking or crushing by allowing the crown to strike the sole of another club when inserting the oversized metal club head into the golf bag.
Another disadvantage of conventional metal woods and oversized metal woods is crystallization of the head packing material causing the club head to rattle. The shaft penetrates the hollow metal club head and transmits vibrational energy to the packing material adjacent the shaft. This vibrational energy can crystallize the packing material. Crystallized packing material hardens and separates, causing a distracting rattle inside the club head.
Another disadvantage of conventional metal wood club heads is that they are molded or cast with an opening in the bottom or sole portion of the club head. A sole plate is welded over the opening to seal the club head. The sole plate welding seam creates a structural discontinuity at the juncture of the front edge of the sole plate and bottom edge of the face plate. This structural discontinuity or weld seam may be subject to failure as the face strikes the ball or the sole strikes the ground. The weld also increases the weight of the bottom portion or sole of the club. The increased weight and metal in the sole means that weight and less metal may be placed in the crown. The crown must, therefore, be thinner and more susceptible to the crushing or cracking by forces acting normal to the crown surface.
Another disadvantage of oversized metal wood club heads is that the ball striking face on these clubs is thinner due to the weight restriction, therefore, susceptible to structural failure by crushing or deformation when striking a ball. Increasing the mass of the club face by increasing the thickness of the face results in a rigid club face and the undesirable effect of a limiting the sweet spot. A thinner face is more flexible. Moreover, a thin club face with perimeter weighting achieves a larger sweet spot. Also there is a weight limit on the amount of metal a design can allocate to the club face without increasing the overall weight of the club head and reducing the club head velocity.